For loop splines amplified ! , why? How can I stop it?
I FOUND THE SOLUTION!!!
I resume the problem to be sure to be helpful:
you have a dataframe or 2 list of points , and you need to connect pairs of points. the faster way is to create splines between them but ....
..in my case blender was generating the connection in different position than expected and unexpected lengths ... but not really randomly .
The problem was  bpy.context.scene.cursor.location  that was not in the center of the world origin
The solution is to reset at every loop the position of the cursor in the center of the world origin.